This invention relates to the field of actuator mechanisms and circuit breakers and more particularly relates to actuator mechanisms and circuit breakers incorporating shape memory alloys.
Various relays, circuit breakers, thermostatic switches and other electromechanical devices have been proposed utilizing shape memory alloys. Among these are: Perry U.S. Pat. No. 3,483,360; Willson U.S. Pat. No. 3,594,674; Willson et al U.S. Pat. Nos. 3,613,732; 3,634,803; and 3,652,969; Du Rocher U.S. Pat. Nos. 3,676,815 and 3,707,694; Hickling U.S. Pat. No. 3,849,756; Clarke U.S. Pat. No. 3,872,415; Jost et al U.S. Pat. No. 3,968,380; Melton et al U.S. Pat. No. 4,205,293; Brubaker U.S. Pat. No. 4,517,543; and Sims U.K. Patent Application No. 2,026,246A.
These devices typically take advantage of the shape memory effect to trip a switch or break a contact upon reaching a critical temperature.
The phenomenon of shape memory is, of course, well known. The ability to possess shape memory is a result of the fact that the shape memory alloy undergoes a reversible transformation from an austenitic state to a martensitic state with a change in temperature. An article made of such an alloy is easily deformed from its original configuration to a new configuration when cooled below the temperature at which the alloy is transformed from the austenitic state to the martensitic state. The temperature at which this transformation begins is usually referred to as the M.sub.s temperature and the temperature at which this transformation is complete is the M.sub.f temperature. When an article thus deformed is warmed to the temperature at which the alloy starts to revert back to austenite, referred to as the A.sub.s temperature, the deformed object will begin to return to its original configuration. The reversion of the alloy will be complete upon reaching the A.sub.f temperature.
Notwithstanding the past efforts devoted to developing electromechanical devices, including those incorporating various shape memory alloys, there has arisen the need for an electromechanical device, in particular a circuit breaker, which is relatively small in size, compact and suitable for use under low amperage (1/2 amp or less) as well as high amperage conditions. It would be highly desirable for this electromechanical device to have low insertion loss. Until the present invention, such a device did not exist.
Accordingly, it is an object of the invention to have an electromechanical device which is relatively small in size, compact and suitable for use under low amperage as well as high amperage conditions.
It is a further object of the invention to have such an electromechanical device for use as a circuit breaker.
It is yet another object of the invention to have such an electromechanical device for use as a circuit breaker having low insertion loss.
These and other objects of the invention will become more apparent after referring to the following description considered in conjunction with the accompanying drawings.